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Most Cannabis Products in Colorado Have Less THC Than Advertised, Study Suggests

By Leo Bear-McGuinness

Published: Apr 14, 2023   
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Recreational cannabis products in Colorado may not be as potent as they appear, according to a new study published in PLOS One.

After going on a shopping spree around the state and buying 23 products from 10 dispensaries, researchers from the University of Northern Colorado had the products tested at a commercial cannabis lab – and the results were at odds with the products’ labels.

Eighteen of the 23 products (78.3%) had less THC % by dry weight than the lowest value reported on the label.

Although the researchers can’t be sure why their results were different to the advertised potencies, they posit that a lack of standardized testing protocols among Colorado’s labs, limited regulatory oversight, and financial incentives to market high THC products likely all play a role.

Getting low in Colorado

To begin their study, the researchers bought 23 products representing 12 different strains from 10 dispensaries across three cities in Colorado, Denver, Garden City, and Fort Collins.

These products were then tested at Mile High Labs in Loveland, CO, for total THC %, by dry weight, using high performance liquid chromatography (HPLC).

“The methods we used followed methods that have been developed for testing THC in flower using HPLC, which is what testing labs should be doing too,” Anna Schwabe, PhD, one of the co-authors of the study, told Analytical Cannabis.

The average observed THC potency was 23.1% lower than the lowest label reported values and 35.6% lower than the highest label reported values.

Sixteen of the 23 products (69.6%) had observed values that were more than 15% lower relative to the lowest reported THC % by dry weight, and 13 of those products (56.5%) were more than 30% lower than the reported value.

Schwabe and her colleagues can’t say for certain why their results were significantly lower than the ones advertised on the products’ labels, although they say that sampling issues, among other issues, may be to blame.

“A representative sample for a batch should contain flowers from high, middle and lower locations from several plants,” Schwabe told Analytical Cannabis.

“The batch should be homogenized for testing, and the results should land somewhere between what the THC is in the top flowers and the bottom flowers. However, what we saw was all the flower in our tests were much lower than the reported number or ranges.”

“We have confidence that our methods were accurate,” she added, “and that the inflated levels of THC observed on packages is either lab manipulation or sampling protocol manipulation.”

THC inflation and lab shopping

This “lab manipulation” issue often goes by another name, lab shopping. This phrase describes the practice when a cannabis producer offers (shops) a cannabis product to different testing labs and then ultimately partners with the lab that offers the highest THC results.

Given the consumer appetite for high THC products, lab shopping has become a blight on the cannabis industry, even in Colorado, one of the oldest legal markets in the country.

Speaking to Analytical Cannabis earlier this year, one former director of a state cannabis lab said that the rise in lab shopping ultimately led to the closure of their business, after they lost multiple clients to competitors that were apparently willing to inflate THC numbers.

“The issue of lab shopping has always existed,” Liz Mason, former director of operations at Aurum Labs, a cannabis testing facility in Durango, CO, said. “And this year [2022], it just became more commonplace behavior.”

Schwabe and her fellow researchers say that, to combat lab shopping and ensure consumers are buying honest products, regulations – such as sampling regulations – will have to change.

“No one is checking to make sure sampling is done correctly and that the samples being sent are in fact representative of the entire batch, as opposed to sending in only apical colas which have the highest amount of THC,” Schwabe told Analytical Cannabis.

“There is limited regulatory oversight,” she added. “No one is actually checking that these testing labs are generating accurate results.”


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